1. Field of the Invention
The present invention relates to an image forming apparatus, a paper sheet processing apparatus or a paper sheet stacking apparatus that is coupled to an image forming system or the like, which is provided with an image forming apparatus and a paper sheet processing apparatus.
In addition, the present invention is further relates to a technology for controlling a paper sheet stacking operation, which makes it possible to appropriately manage a full loaded condition without generating an overloaded status caused by an overweight, with respect to various kinds of paper sheets, which are different from each other in weight and thickness thereof.
2. Description of Related Art
An image forming apparatus, such as a laser printer, a copier, etc., is provided with a stacking apparatus, which is disposed in the vicinity of an ejection opening so as to stack paper sheets ejected outside from the concerned apparatus, thereon. In the stacking apparatus above-mentioned, the stacking tray is configured to descend every time when each of the paper sheets is stacked onto the stacking tray, so that an upper surface of the bunch of paper sheets, currently stacked on the stacking tray, coincides with a predetermined position (height) of the ejecting section. Further, at the time when a part of the paper sheets, currently stacked on the stacking tray, is removed, the stacking tray is controlled to elevate, so that an upper surface of paper sheets, stacked on the stacking tray, coincides with a predetermined position of the ejecting section.
In the process of the consecutive actions above-mentioned, the descended position of the stacking tray is detected by sensors. Then, at the time when the stacking tray arrives at the predetermined descended position established in advance, it is determined that the stacking tray enters into the full loaded condition. Based on the above-mentioned determination in regard to the full loaded condition, the stacking tray is prevented from entering into the overloaded status caused by further stacking the paper sheets thereon.
With respect to the paper sheet stacking operation above-mentioned, each of Japanese Patent Application Laid-Open Publication 2011-121663, Japanese Patent Application Laid-Open Publication 2009-249080 and Japanese Patent Application Laid-Open Publication 2007-15824, sets forth various kinds of the related technologies.
In the paper sheet stacking apparatus as above-mentioned, at the time when a full-loaded conditional position sensor detects the fact that the stacking tray has descended to the lowest point, it is determined that a current status is the full loaded condition. In this connection, as the definition of the full loaded condition above-mentioned, the position of the full-loaded conditional position sensor is established at such a position that makes it possible to stack a predetermined number of paper sheets, acquired by back-calculating a stackable number of specific paper sheets from a total stackable weight of the specific paper sheets, a usage frequency of which is presumably the highest among other kinds of paper sheets. In a case where the usage frequency of normal paper sheets whose sizes are A4 size (hereinafter, each referred to as an A4 paper sheet or an A4 paper, further, in regard to other sizes, referred to as a B4 paper sheet, an A3 paper sheet, . . . , as well) is the highest, the full-loaded conditional position sensor is disposed at such a position that makes it possible to stack, for instance, 4000 sheets of A4 papers, acquired by back-calculating from a total weight of the paper sheets being stackable on the stacking tray concerned.
However, sometimes, paper sheets being larger than the A4 paper sheet, for instance, B4 paper sheets, A3 paper sheets, etc., or other paper sheets, a specific weight of each of which is greater than that of the A4 paper sheet, such as a pigment coated paper sheet or the like, may be employed. In this case, at the time when the full-loaded conditional position sensor detects the full loaded status, an actually loaded weight may exceed the total stackable weight of the specific paper sheets. For this reason, depending on a kind of paper sheets actually employed, sometimes, the stacking tray and/or the elevation driving mechanism may suffer from a large amount of loaded or driving burden. Conversely, in a case where paper sheets, each being smaller than the A4 paper sheet, are to be employed, the full-loaded conditional position sensor may detect the full loaded status even when an allowable room of the total stackable weight still remains. In other words, the system or the apparatus may enter into such a status that the allowable room of the total stackable weight still exists in vain.
According to Japanese Patent Application Laid-Open Publication 2011-121663 above-cited, the apparatus is provided with a reference height detecting section that detects the paper-sheet stacking height at the “reference height” located at a position being lower than the full loaded height of the ejecting tray. Then, after detecting the paper sheets stacked on the ejecting tray, the reference height detecting section accumulates the thickness values of the paper sheets, which are to be ejected newly as a group. Then, based on the accumulated value above-found, the full load processing is implemented.
Accordingly, since the reference height is detected from the paper sheet stacking height (or the stacking height of the group of paper sheets), and then, the residual height (number of paper sheets) is calculated from the reference height, it becomes possible to minimize the difference between the actual height of the group of paper sheets and the calculated value, resulting in improvements of preciseness and accuracy aspects. However, since the maximum weight to be loaded onto the ejecting tray is out of the considerations, it may be inevitable to enter into the overweight state caused by the overload, depending on the kind of paper sheets concerned. In other words, the aforementioned subject is not solved.
According to Japanese Patent Application Laid-Open Publication 2009-249080 above-cited, the apparatus is provided with a plurality of loaded condition detecting sections, so that, when any one of the loaded condition detecting sections detects the stacking device, the operation for determining whether or not the stacked paper sheets are in the full loaded condition is implemented. Further, it is proposed in the Patent Document above-cited that the above-mentioned determination should be made on the basis of a kind of the paper sheets. Accordingly, at the time when any one of the loaded condition detecting sections detects the stacking device, it is determined whether or not the stacked paper sheets are currently in the full loaded condition, based on the kind of the paper sheets concerned. Thanks to the above-mentioned, it becomes possible not only to prevent paper sheets, each having a relatively heavy weight, from being massively stacked onto the stacking device, but also, to prevent the paper sheets from being excessively stacked onto the stacking device. Accordingly, it becomes unnecessary to heighten the strength of the stacking device, and it also becomes unnecessary to increase the driving power for the descending mechanism, resulting in reduction of the manufacturing cost thereof.
However, according to the Patent Document above-cited, the sensor for detecting the full loaded condition is determined on the basis of the kind of the paper sheet. For this reason, the above-disclosed controlling operation is absolutely conducted on the basis of a subjective degree of a weight difference between normal paper sheets and relatively heavy paper sheets. As a result, the aforementioned subjects, at least one of which is to prevent the stacking tray from entering into the overweight condition and/or to stack paper sheets up to the maximum stackable weight with zero waste, cannot be solved.
For instance, even if it is possible to change the detecting device by considering the size difference between the kinds of paper sheets, such as that between an A4 paper sheet and a B4 paper sheet or the like, there exists no absolute criterion, though it is possible to cope with the above-mentioned operation for changing the detecting device by employing a relative criterion. Accordingly, in a case where there exists such an A4 paper sheet that is heavier than a B4 paper sheet, for instance, in a case where not only a normal paper sheet, but also a thin-and-heavy paper sheet, such as a pigment coated sheet, etc., are to be employed, or the like, there has arisen such a problem that it is impossible to appropriately cope with such the cases.
According to Japanese Patent Application Laid-Open Publication 2007-15824 above-cited, by making the ejecting tray move in both up and down directions, a moving velocity of the tray driving action, a moving time and an overweight of stacked paper sheets measured by the weight scale device, are detected in conjunction with the above up-and-down moving actions. Then, it is proposed that, when the overweight status of stacked paper sheets is detected and it is determined that the weight of paper sheets, currently stacked on the ejecting tray concerned, reaches the predetermined allowable value, the stacking action is made to stop.
According to the consecutive operations above-mentioned, since the control device determines the weight status of the paper sheets, currently stacked on the ejecting tray concerned, it is possible to control the loading condition of the driving section in the process of moving the paper sheet stacking section in the up and down directions, more accurately than in the case of determining the stacking height of the paper sheets concerned. Further, even when an error of measuring the paper-sheet stacking height is great, it is possible to accurately determine the loading condition of the driving section so as to make it possible to control the stacking amount of paper sheets.
However, in order to determine the stacking weight from the moving velocity and/or the moving time in midcourse of elevating and descending operations, it is necessary to repeatedly conduct elevating and descending actions for a predetermined moving distance (for instance, 40 mm), every time when a predetermined number of paper sheets (for instance, 5 paper sheets) are ejected. This kind of repeated operation of elevating and descending actions may adversely affect the overall operations of the apparatus from a power consumption, sound noise and a durability points of view.
Further, it may be considered such a measure that a number of paper sheets to be ejected are counted, and then, a weight of paper sheets, currently stacked, is calculated by accumulating the number of the paper sheets and the weight of the paper sheets so as to stack the paper sheets within the range of the maximum stackable weight. However, in case that some paper sheets are removed from the stacking section in midcourse of implementing the stacking operation, it is impossible to count the number of removed paper sheets. For this reason, the control section may erroneously determine, from the calculation result above-mentioned, that the weight of paper sheets, currently stacked on the ejecting tray concerned, reaches the maximum stackable weight at the time when the weight of paper sheets does not actually reach the maximum stackable weight. Then, owing to the determination error above-mentioned, the stacking operation may be made to stop in a state of still remaining a room for stacking more number of paper sheets.